/*
 *      w1_ds28e04.c - w1 family 1C (DS28E04) driver
 *
 * Copyright (c) 2012 Markus Franke <franke.m@sebakmt.com>
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2. See the file COPYING for more details.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/crc16.h>
#include <linux/uaccess.h>

#define CRC16_INIT              0
#define CRC16_VALID             0xb001

#include <linux/w1.h>

#define W1_FAMILY_DS28E04       0x1C

/* Allow the strong pullup to be disabled, but default to enabled.
 * If it was disabled a parasite powered device might not get the required
 * current to copy the data from the scratchpad to EEPROM.  If it is enabled
 * parasite powered devices have a better chance of getting the current
 * required.
 */
static int w1_strong_pullup = 1;
module_param_named(strong_pullup, w1_strong_pullup, int, 0);

/* enable/disable CRC checking on DS28E04-100 memory accesses */
static char w1_enable_crccheck = 1;

#define W1_EEPROM_SIZE          512
#define W1_PAGE_COUNT           16
#define W1_PAGE_SIZE            32
#define W1_PAGE_BITS            5
#define W1_PAGE_MASK            0x1F

#define W1_F1C_READ_EEPROM      0xF0
#define W1_F1C_WRITE_SCRATCH    0x0F
#define W1_F1C_READ_SCRATCH     0xAA
#define W1_F1C_COPY_SCRATCH     0x55
#define W1_F1C_ACCESS_WRITE     0x5A

#define W1_1C_REG_LOGIC_STATE   0x220

struct w1_f1C_data {
        u8      memory[W1_EEPROM_SIZE];
        u32     validcrc;
};

/**
 * Check the file size bounds and adjusts count as needed.
 * This would not be needed if the file size didn't reset to 0 after a write.
 */
static inline size_t w1_f1C_fix_count(loff_t off, size_t count, size_t size)
{
        if (off > size)
                return 0;

        if ((off + count) > size)
                return size - off;

        return count;
}

static int w1_f1C_refresh_block(struct w1_slave *sl, struct w1_f1C_data *data,
                                int block)
{
        u8      wrbuf[3];
        int     off = block * W1_PAGE_SIZE;

        if (data->validcrc & (1 << block))
                return 0;

        if (w1_reset_select_slave(sl)) {
                data->validcrc = 0;
                return -EIO;
        }

        wrbuf[0] = W1_F1C_READ_EEPROM;
        wrbuf[1] = off & 0xff;
        wrbuf[2] = off >> 8;
        w1_write_block(sl->master, wrbuf, 3);
        w1_read_block(sl->master, &data->memory[off], W1_PAGE_SIZE);

        /* cache the block if the CRC is valid */
        if (crc16(CRC16_INIT, &data->memory[off], W1_PAGE_SIZE) == CRC16_VALID)
                data->validcrc |= (1 << block);

        return 0;
}

static int w1_f1C_read(struct w1_slave *sl, int addr, int len, char *data)
{
        u8 wrbuf[3];

        /* read directly from the EEPROM */
        if (w1_reset_select_slave(sl))
                return -EIO;

        wrbuf[0] = W1_F1C_READ_EEPROM;
        wrbuf[1] = addr & 0xff;
        wrbuf[2] = addr >> 8;

        w1_write_block(sl->master, wrbuf, sizeof(wrbuf));
        return w1_read_block(sl->master, data, len);
}

static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
                           struct bin_attribute *bin_attr, char *buf,
                           loff_t off, size_t count)
{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
        struct w1_f1C_data *data = sl->family_data;
        int i, min_page, max_page;

        count = w1_f1C_fix_count(off, count, W1_EEPROM_SIZE);
        if (count == 0)
                return 0;

        mutex_lock(&sl->master->mutex);

        if (w1_enable_crccheck) {
                min_page = (off >> W1_PAGE_BITS);
                max_page = (off + count - 1) >> W1_PAGE_BITS;
                for (i = min_page; i <= max_page; i++) {
                        if (w1_f1C_refresh_block(sl, data, i)) {
                                count = -EIO;
                                goto out_up;
                        }
                }
                memcpy(buf, &data->memory[off], count);
        } else {
                count = w1_f1C_read(sl, off, count, buf);
        }

out_up:
        mutex_unlock(&sl->master->mutex);

        return count;
}

/**
 * Writes to the scratchpad and reads it back for verification.
 * Then copies the scratchpad to EEPROM.
 * The data must be on one page.
 * The master must be locked.
 *
 * @param sl    The slave structure
 * @param addr  Address for the write
 * @param len   length must be <= (W1_PAGE_SIZE - (addr & W1_PAGE_MASK))
 * @param data  The data to write
 * @return      0=Success -1=failure
 */
static int w1_f1C_write(struct w1_slave *sl, int addr, int len, const u8 *data)
{
        u8 wrbuf[4];
        u8 rdbuf[W1_PAGE_SIZE + 3];
        u8 es = (addr + len - 1) & 0x1f;
        unsigned int tm = 10;
        int i;
        struct w1_f1C_data *f1C = sl->family_data;

        /* Write the data to the scratchpad */
        if (w1_reset_select_slave(sl))
                return -1;

        wrbuf[0] = W1_F1C_WRITE_SCRATCH;
        wrbuf[1] = addr & 0xff;
        wrbuf[2] = addr >> 8;

        w1_write_block(sl->master, wrbuf, 3);
        w1_write_block(sl->master, data, len);

        /* Read the scratchpad and verify */
        if (w1_reset_select_slave(sl))
                return -1;

        w1_write_8(sl->master, W1_F1C_READ_SCRATCH);
        w1_read_block(sl->master, rdbuf, len + 3);

        /* Compare what was read against the data written */
        if ((rdbuf[0] != wrbuf[1]) || (rdbuf[1] != wrbuf[2]) ||
            (rdbuf[2] != es) || (memcmp(data, &rdbuf[3], len) != 0))
                return -1;

        /* Copy the scratchpad to EEPROM */
        if (w1_reset_select_slave(sl))
                return -1;

        wrbuf[0] = W1_F1C_COPY_SCRATCH;
        wrbuf[3] = es;

        for (i = 0; i < sizeof(wrbuf); ++i) {
                /* issue 10ms strong pullup (or delay) on the last byte
                   for writing the data from the scratchpad to EEPROM */
                if (w1_strong_pullup && i == sizeof(wrbuf)-1)
                        w1_next_pullup(sl->master, tm);

                w1_write_8(sl->master, wrbuf[i]);
        }

        if (!w1_strong_pullup)
                msleep(tm);

        if (w1_enable_crccheck) {
                /* invalidate cached data */
                f1C->validcrc &= ~(1 << (addr >> W1_PAGE_BITS));
        }

        /* Reset the bus to wake up the EEPROM (this may not be needed) */
        w1_reset_bus(sl->master);

        return 0;
}

static ssize_t eeprom_write(struct file *filp, struct kobject *kobj,
                            struct bin_attribute *bin_attr, char *buf,
                            loff_t off, size_t count)

{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
        int addr, len, idx;

        count = w1_f1C_fix_count(off, count, W1_EEPROM_SIZE);
        if (count == 0)
                return 0;

        if (w1_enable_crccheck) {
                /* can only write full blocks in cached mode */
                if ((off & W1_PAGE_MASK) || (count & W1_PAGE_MASK)) {
                        dev_err(&sl->dev, "invalid offset/count off=%d cnt=%zd\n",
                                (int)off, count);
                        return -EINVAL;
                }

                /* make sure the block CRCs are valid */
                for (idx = 0; idx < count; idx += W1_PAGE_SIZE) {
                        if (crc16(CRC16_INIT, &buf[idx], W1_PAGE_SIZE)
                                != CRC16_VALID) {
                                dev_err(&sl->dev, "bad CRC at offset %d\n",
                                        (int)off);
                                return -EINVAL;
                        }
                }
        }

        mutex_lock(&sl->master->mutex);

        /* Can only write data to one page at a time */
        idx = 0;
        while (idx < count) {
                addr = off + idx;
                len = W1_PAGE_SIZE - (addr & W1_PAGE_MASK);
                if (len > (count - idx))
                        len = count - idx;

                if (w1_f1C_write(sl, addr, len, &buf[idx]) < 0) {
                        count = -EIO;
                        goto out_up;
                }
                idx += len;
        }

out_up:
        mutex_unlock(&sl->master->mutex);

        return count;
}

static BIN_ATTR_RW(eeprom, W1_EEPROM_SIZE);

static ssize_t pio_read(struct file *filp, struct kobject *kobj,
                        struct bin_attribute *bin_attr, char *buf, loff_t off,
                        size_t count)

{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
        int ret;

        /* check arguments */
        if (off != 0 || count != 1 || buf == NULL)
                return -EINVAL;

        mutex_lock(&sl->master->mutex);
        ret = w1_f1C_read(sl, W1_1C_REG_LOGIC_STATE, count, buf);
        mutex_unlock(&sl->master->mutex);

        return ret;
}

static ssize_t pio_write(struct file *filp, struct kobject *kobj,
                         struct bin_attribute *bin_attr, char *buf, loff_t off,
                         size_t count)

{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
        u8 wrbuf[3];
        u8 ack;

        /* check arguments */
        if (off != 0 || count != 1 || buf == NULL)
                return -EINVAL;

        mutex_lock(&sl->master->mutex);

        /* Write the PIO data */
        if (w1_reset_select_slave(sl)) {
                mutex_unlock(&sl->master->mutex);
                return -1;
        }

        /* set bit 7..2 to value '1' */
        *buf = *buf | 0xFC;

        wrbuf[0] = W1_F1C_ACCESS_WRITE;
        wrbuf[1] = *buf;
        wrbuf[2] = ~(*buf);
        w1_write_block(sl->master, wrbuf, 3);

        w1_read_block(sl->master, &ack, sizeof(ack));

        mutex_unlock(&sl->master->mutex);

        /* check for acknowledgement */
        if (ack != 0xAA)
                return -EIO;

        return count;
}

static BIN_ATTR_RW(pio, 1);

static ssize_t crccheck_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        if (put_user(w1_enable_crccheck + 0x30, buf))
                return -EFAULT;

        return sizeof(w1_enable_crccheck);
}

static ssize_t crccheck_store(struct device *dev, struct device_attribute *attr,
                              const char *buf, size_t count)
{
        char val;

        if (count != 1 || !buf)
                return -EINVAL;

        if (get_user(val, buf))
                return -EFAULT;

        /* convert to decimal */
        val = val - 0x30;
        if (val != 0 && val != 1)
                return -EINVAL;

        /* set the new value */
        w1_enable_crccheck = val;

        return sizeof(w1_enable_crccheck);
}

static DEVICE_ATTR_RW(crccheck);

static struct attribute *w1_f1C_attrs[] = {
        &dev_attr_crccheck.attr,
        NULL,
};

static struct bin_attribute *w1_f1C_bin_attrs[] = {
        &bin_attr_eeprom,
        &bin_attr_pio,
        NULL,
};

static const struct attribute_group w1_f1C_group = {
        .attrs          = w1_f1C_attrs,
        .bin_attrs      = w1_f1C_bin_attrs,
};

static const struct attribute_group *w1_f1C_groups[] = {
        &w1_f1C_group,
        NULL,
};

static int w1_f1C_add_slave(struct w1_slave *sl)
{
        struct w1_f1C_data *data = NULL;

        if (w1_enable_crccheck) {
                data = kzalloc(sizeof(struct w1_f1C_data), GFP_KERNEL);
                if (!data)
                        return -ENOMEM;
                sl->family_data = data;
        }

        return 0;
}

static void w1_f1C_remove_slave(struct w1_slave *sl)
{
        kfree(sl->family_data);
        sl->family_data = NULL;
}

static struct w1_family_ops w1_f1C_fops = {
        .add_slave      = w1_f1C_add_slave,
        .remove_slave   = w1_f1C_remove_slave,
        .groups         = w1_f1C_groups,
};

static struct w1_family w1_family_1C = {
        .fid = W1_FAMILY_DS28E04,
        .fops = &w1_f1C_fops,
};
module_w1_family(w1_family_1C);

MODULE_AUTHOR("Markus Franke <franke.m@sebakmt.com>, <franm@hrz.tu-chemnitz.de>");
MODULE_DESCRIPTION("w1 family 1C driver for DS28E04, 4kb EEPROM and PIO");
MODULE_LICENSE("GPL");
MODULE_ALIAS("w1-family-" __stringify(W1_FAMILY_DS28E04));